Particulate-loaded polymer fibers and extrusion methods

ABSTRACT

Particulate-loaded polymer fibers along with methods and systems for extruding polymeric fibers are disclosed. The particulate-loaded polymer fibers have a fiber body that includes a polymeric binder with a plurality of particles distributed within the polymeric binder. Some of the particles are completely encapsulated within the polymeric binder and others may be embedded such that they are partially exposed on the outer surface of the fiber body. The polymers used in the fibers may be of high molecular weight and the encapsulated particles may be preferentially distributed towards the outer surfaces of the fibers.

FIELD OF THE INVENTION

The present invention relates to the field of particulate-loaded polymerfibers along with extrusion processing and apparatus for manufacturingthe same.

BACKGROUND OF THE INVENTION

Conventional fiber forming methods and apparatus typically involves theextrusion of polymeric material through orifices. The rates, pressuresand temperatures of the typical fiber extrusion process represent acompromise between economic requirements and the physicalcharacteristics of the polymeric material. For example, the molecularweight of the polymeric material is directly tied to both melt viscosityand polymeric material performance. Unfortunately, improvements inpolymeric material performance are conventionally tied to increasedmolecular weight and corresponding relatively high melt viscosities. Thehigher melt viscosities typically result in slower, less economicallyviable processes for forming fibers.

To address the high melt viscosities of higher molecular weightpolymers, conventional processes may rely on relatively high temperatureprocessing in an effort to lower the melt viscosity of the polymericmaterial. The process temperature may typically, however, be limited bydegradation of the polymeric material at higher temperatures. Inconjunction with increased process temperatures, the process pressures,i.e., the pressure at which the polymer is extruded, may also beincreased to improve process speed. Process pressure may, however, belimited by the equipment employed to extrude the fibers. As a result,the processing speed in conventional processes is typically constrainedby the factors discussed above.

In view of the issues discussed above, the conventional strategy inextruding molten polymer for fiber making is to reduce the molecularweight of the polymeric material to attain economically viableprocessing rates. The reduced molecular weight results in acorresponding compromise in material properties of the extrudedpolymeric fibers.

To at least partially address the compromises in material properties ofconventional extruded fibers, the fiber strength may be improved byorienting the polymeric material in the fiber. Orientation is impartedby pulling or stretching the fiber after it exits the extrusion die. Asa result, the polymeric material used for the fibers typically must havea substantial tensile stress carrying capability in the semi-moltenstate in which the polymeric material exits the die (or the fibers willmerely break when pulled). Such properties are conventionally availablein semi-crystalline polymers such as, e.g., polyethylene, polypropylene,polyesters, and polyamides. Thus, conventional fiber extrusion processescan be performed with only a limited number of polymeric materials.

SUMMARY OF THE INVENTION

The present invention provides particulate-loaded polymer fibers alongwith methods and systems for extruding polymeric fibers.

The particulate-loaded polymer fibers have a fiber body that includes apolymeric binder with a plurality of particles distributed within thepolymeric binder. Some of the particles are completely encapsulatedwithin the polymeric binder and others may be partially exposed on theouter surface of the fiber body.

Among the potential advantages of particulate-loaded fibers of thepresent invention is that the polymeric fiber body can be formed ofpolymers with relatively low melt flow index or relatively high meltviscosity (and corresponding high molecular weight as discussed herein).As a result, the potential benefits associated with fibers manufacturedusing such polymers in methods of the present invention may also beavailable for particulate-loaded fibers.

Another potential advantage of the present invention is that theparticles within the fiber body may preferably be distributed such thatthe particle density (i.e., the number of particles per unit volume ofthe fiber body) is higher proximate the outer surface of the fiber. Thatdistribution of particles within the fiber may be advantageous forenhancing fiber strength (by, e.g., providing a central core thatincludes fewer particles).

The particle distribution profile may also be advantageous in situationswhere it is desired that the particles be encapsulated near the outersurface of the fiber or partially exposed on the outer surface of thefiber. This may be particularly true in situations in which it isbeneficial if additional particles are exposed as portions of thepolymeric binder are removed during use (as may happen in, e.g., fibersused in abrasive articles, etc.).

Another potential advantage of the particle distribution seen inmelt-extruded fibers of the present invention is that the amount ofparticles needed to provide a selected particle density proximate theouter surface of the fiber may be reduced because the particles arepreferentially distributed proximate the outer surface of the fiber.

The extrusion process used to manufacture the fibers may preferablyinvolve the delivery of a lubricant separately from a polymer meltstream to each orifice of an extrusion die such that the lubricantpreferably encases the polymer melt stream as it passes through the dieorifice. The use of a lubricant delivered separately from the polymermelt stream in a polymeric fiber extrusion process can provide a numberof potential advantages.

For example, the use of separately-delivered lubricant can provide fororiented polymeric fibers in the absence of pulling, i.e., in someembodiments it may not be necessary to pull or stretch the fiber afterit exits the die to obtain an oriented polymeric fiber. If the polymericfibers are not pulled after extrusion, they need not exhibit substantialtensile stress-carrying capability in the semi-molten state that theyare in after exiting the die. Instead, the lubricated extrusion methodsof the present invention can, in some instances, impart orientation tothe polymeric material as it moves through the die such that thepolymeric material may preferably be oriented before it exits the die.

One potential advantage of reducing or eliminating the need for pullingor stretching to impart orientation is that the candidate polymericmaterials for extruding polymeric fibers can be significantly broadenedto include polymeric materials that might not otherwise be used forextruded fibers. Heterophase polymers may also be extruded into anoriented fiber via the proposed method. Composite fiber constructionssuch as ‘sheath/core’ or ‘islands-in-the-sea’ or ‘pie’ or ‘hollow pie’are also compatible with this method.

Potential advantages of the methods of the present invention mayinclude, e.g., the ability to extrude multiple polymeric fiberssimultaneously at relatively low pressures. The relatively low pressuresmay result in cost savings in terms of equipment and process costs.

For the purposes of the present invention, the term “fiber” (andvariations thereof) means a slender, threadlike structure or filamentthat has a substantially continuous length relative to its width, e.g.,a length that is at least 1000 times its width. The width of the fibersof the present invention may preferably be limited to a maximumdimension of 5 millimeters or less, preferably 2 millimeters or less,and even more preferably 1 millimeter or less.

The fibers of the present invention may be monocomponent fibers;bicomponent or conjugate fibers (for convenience, the term “bicomponent”will often be used to mean fibers that consist of two components as wellas fibers that consist of more than two components); and fiber sectionsof bicomponent fibers, i.e., sections occupying part of thecross-section of and extending over the length of the bicomponentfibers.

Another potential advantage of some embodiments of the present inventionmay be found in the ability to extrude polymers with a low Melt FlowIndex (MFI). In conventional polymeric fiber extrusion processes, theMFI of the extruded polymers is about 35 or higher. Using the methods ofthe present invention, the extrusion of polymeric fibers can be achievedusing polymers with a MFI of 30 or less, in some instances 10 or less,in other instances 1 or less, and in still other instances 0.1 or less.Before the present invention, extrusion processing of such highmolecular weight (low MFI) polymers to form fibers was typicallyperformed with the use of solvents to dissolve the polymers therebyreducing their viscosity. Such methods carried with them the difficultyof dissolving the high molecular polymers and then removing the solvent(including disposal or recycling). Examples of low melt flow indexpolymers that may potentially be used in connection with the presentinvention may include LURAN S 757 (ASA, 8.0 MFI) available from BASFCorporation of Wyandotte, Mich.; P4G2Z-026 (PP, 1.0 MFI) available fromHuntsman Polymers of Houston, Tex.; FR PE 152 (HDPE, 0.1 MFI) availablefrom PolyOne Corporation of Avon Lake, Ohio; 7960.13 (HDPE, 0.06 MFI)available from ExxonMobil Chemical of Houston Tex.; and ENGAGE 8100(ULDPE, 1.0 MFI) available from ExxonMobil Chemical of Houston Tex.

Another potential advantage of some methods of the present invention mayinclude the relatively high mass flow rates that may be achieved. Forexample, using the methods of the present invention, it may be possibleto extrude polymeric material into fibers at rates of 10 grams perminute or higher, in some instances 100 grams per minute or higher, andin other instances at rates of 400 grams per minute or higher. Thesemass flow rates may be achieved through an orifice having an area of 0.2square millimeters (mm²) or less.

Still another potential advantage of some methods of the presentinvention may include the ability to extrude polymeric fibers thatinclude orientation at the molecular level that may, e.g., enhance thestrength or provide other advantageous mechanical, optical, etc.properties. If the polymeric fibers are constructed of amorphouspolymers, the amorphous polymeric fibers may optionally be characterizedas including portions of rigid or ordered amorphous polymer phases ororiented amorphous polymer phases (i.e., portions in which molecularchains within the fiber are aligned, to varying degrees, generally alongthe fiber axis).

Although oriented polymeric fibers are known, the orientation isconventionally achieved by pulling or drawing the fibers as they exit adie orifice. Many polymers cannot, however, be pulled after extrusionbecause they do not possess sufficient mechanical strength immediatelyafter extrusion in the molten or semi-molten state to be pulled withoutbreaking. The methods of the present invention can, however, eliminatethe need to draw polymeric fibers to achieve orientation because thepolymeric material may be oriented within the die before it exits theorifice. As a result, oriented fibers may be extruded using polymersthat could not conventionally be extruded and drawn in a commerciallyviable process.

In some methods of the present invention, it may be preferably tocontrol the temperature of the lubricant, the die, or both the lubricantand the die to quench the polymeric material such that the orientationis not lost or is not significantly reduced due to relaxation outside ofthe die. In some instances, the lubricant may be selected based, atleast in part, on its ability to quench the polymeric material by, e.g.,evaporation.

In one aspect, the present invention provides a particulate-loadedpolymeric fiber having a fiber body that includes a polymeric binder anda plurality of particles encapsulated within the polymeric binder,wherein the polymeric binder consists essentially of one or morepolymers, and wherein the encapsulated particles have an encapsulatedparticle density, and wherein the encapsulated particle density ishigher proximate an outer surface of the fiber.

In another aspect, the present invention provides a particulate-loadedpolymeric fiber having a fiber body that includes one or more polymers,and wherein all of the one or more polymers have a melt flow index of 10or less measured at the conditions specified for the one or morepolymers; and a first plurality of particles encapsulated within thefiber body and a second plurality of particles embedded in an outersurface of the fiber body, wherein the encapsulated first plurality ofparticles have an encapsulated particle density, and wherein theencapsulated particle density of the first plurality of particles ishighest proximate an outer surface of the fiber.

In another aspect, the present invention provides a method of making aparticulate-loaded polymeric fiber by entraining a plurality ofparticles within a polymer melt stream; passing the polymer melt streamwith the plurality of particles entrained therein through an orificelocated within a die, wherein the orifice has an entrance, an exit andan interior surface extending from the entrance to the exit, wherein theorifice is a semi-hyperbolic converging orifice, and wherein the polymermelt stream enters the orifice at the entrance and leaves the orifice atthe exit; delivering lubricant to the orifice separately from thepolymer melt stream, wherein the lubricant is introduced at the entranceof the orifice; and collecting the particulate-loaded polymeric fiberincluding the polymer melt stream and a plurality of particlesencapsulated within the polymer melt stream, wherein the encapsulatedparticles comprise an encapsulated particle density within the fiber,and wherein the encapsulated particle density is higher proximate anouter surface of the fiber.

In another aspect, the present invention may provide a method of makinga polymeric fiber by passing a polymer melt stream through an orificelocated within a die, wherein the orifice has an entrance, an exit andan interior surface extending from the entrance to the exit, wherein theorifice is a semi-hyperbolic converging orifice, and wherein the polymermelt stream enters the orifice at the entrance and leaves the orifice atthe exit; delivering lubricant to the orifice separately from thepolymer melt stream, wherein the lubricant is introduced at the entranceof the orifice; and collecting a fiber including the polymer melt streamafter the polymer melt stream leaves the exit of the orifice.

In another aspect, the present invention may provide a method of makinga polymeric fiber by passing a polymer melt stream through an orifice ofa die, wherein the orifice has an entrance, an exit and an interiorsurface extending from the entrance to the exit, wherein the orifice isa semi-hyperbolic converging orifice, wherein the polymer melt streamenters the orifice at the entrance and leaves the orifice at the exit,wherein the polymer melt stream includes a bulk polymer, wherein thebulk polymer is a majority of the polymer melt stream, and wherein thebulk polymer consists essentially of a polymer with a melt flow index of1 or less measured at the conditions specified for the polymer in ASTMD1238; delivering lubricant to the orifice separately from the polymermelt stream; and collecting a fiber including the bulk polymer after thepolymer melt stream leaves the exit of the orifice.

These and other features and advantages of various embodiments of themethods, systems, and articles of the present invention may be describedbelow in connection with various illustrative embodiments of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an idealized enlarged cross-sectional view of oneparticulate-loaded fiber according to the present invention.

FIG. 2 is a schematic diagram illustrating a process window for methodsaccording to the present invention.

FIG. 3 is an enlarged cross-sectional view of a portion of one exemplarydie that may be used in connection with the present invention.

FIG. 4 is an enlarged view of the orifice in the die of FIG. 3.

FIG. 5 is a plan view of a portion of one exemplary extrusion die platethat may be used in connection with the present invention.

FIG. 6 is a schematic diagram of one system including a die according tothe present invention.

FIG. 7 is an enlarged cross-sectional view of another extrusionapparatus that may be used in connection with the present invention.

FIG. 8 is an enlarged plan view of another exemplary die orifice andlubrication channels that may be used in connection with the presentinvention.

FIG. 9 is an enlarged cross-sectional view of one exemplary polymericfiber exiting a die orifice in accordance with the methods of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of illustrative embodiments of theinvention, reference is made to the accompanying figures of the drawingwhich form a part hereof, and in which are shown, by way ofillustration, specific embodiments in which the invention may bepracticed. It is to be understood that other embodiments may be utilizedand structural changes may be made without departing from the scope ofthe present invention.

As discussed above, the present invention provides methods and systemsfor manufacturing polymeric fibers through a lubricated flow extrusionprocess. The present invention also provides particulate-loadedpolymeric fibers that may preferably be manufactured using such systemsand methods.

FIG. 1 is an idealized cross-sectional view of one exemplaryparticulate-loaded fiber 2 in accordance with the present invention. Thefiber 2 is formed with a longitudinal axis 3 extending along its length.The fiber 2 includes a body 4 formed of one or more polymers (sometimesreferred to herein as a polymeric binder). The body 4 extends along thelength of the longitudinal axis 3 and includes an outer surface 5.Although the fiber body 4 depicted in FIG. 1 has a generally circularcross-section shape (taken transverse to the longitudinal axis 3), thefibers of the present invention may take any suitable cross-sectionalshape, e.g., oval, triangular, rectangular, hexagonal, irregular, etc.

The one or more polymers used to form the fiber body 4 may have anycomposition as described herein. For example, it may be preferred thatthe one or more polymers of fiber body 4 have a melt flow index (MFI) 30or less, 10 or less, 1 or less, 0.1 or less, etc.; it may be preferredthat the one or more polymers be semi-crystalline polymers (e.g.,nylon); etc.

Also depicted in connection with FIG. 1 are particles 6 which areencapsulated (where “encapsulated” means that that particles arecompletely contained within the polymer forming the fiber body 4. Inaddition to particles 6 that are encapsulated within the polymeric body4, the fiber 2 may also includes particles 7 that are only embedded (orpartially encapsulated) in the polymer forming the fiber body 4 suchthat a portion of the particle is exposed on the outer surface 5 of thefiber body 4.

Among the particles 6 encapsulated within the body 4, it may bepreferred that the encapsulated particles 6 are distributed within thefiber such that the encapsulated particle density is higher proximatethe outer surface 5 of the fiber 2. As used herein, “encapsulateparticle density” refers to the number of encapsulated particles perunit volume of the fiber. In some embodiments, it may be preferred thatthe encapsulated particle density within the outermost 20% of the volumeof the fiber be two times or more the particle density within theinnermost 20% of the volume of the fiber. Alternatively, it may bepreferred that 50% or more of the encapsulated particles be locatedwithin the outermost 20% of the fiber. In another alternative, it may bepreferred that 90% of the encapsulated particles be located within theoutermost 10% of the volume of the fiber.

The particles 6 (and particles 7 exposed on the outer surface 5) maypreferably be formed of materials that do not readily intermix with ormelt into the polymeric body 4. It may be preferred that the particles 6& 7 be formed of non-polymeric materials (although it should beunderstood that some particles may be used in connection with thepresent invention if their melt processing temperatures (as definedherein) are high enough such that the particles 6 & 7 retain theirseparate and distinct form from the surrounding fiber body 4). Examplesof some potentially suitable non-polymeric particles that may be used inparticulate-loaded fibers of the present invention may include, e.g.,metals, metal oxides (e.g., aluminum oxide), ceramics, glasses,minerals, etc.

In some instances, the particles added to fibers of the presentinvention may include optical functionality as, e.g., retroreflectors,etc. Examples of some potentially suitable optical elements that may beused as particles in connection with the present invention may bedescribed in, e.g., U.S. Pat. Nos. 4,367,919 (Tung et al.); 5,774,265(Mathers et al.); 5,835,271 (Stump et al.); 5,853,851 (Morris), etc.

The particles used in connection with the particulate-loaded fibers ofthe present invention may potentially be characterized on the basis oftheir size. It may be preferred, for example, that the particles besmall enough such that they do not inhibit fiber formation or extrusion(if that is the process by which the fibers are formed). In someinstances, it may be preferred that the particles have a maximumdimension of 1 millimeter or less, 500 micrometers or less, 250micrometers or less, 100 micrometers or less, 50 micrometers or less, or10 micrometers or less. As used herein, “maximum size” of particles isdetermined by screening or sieving such that the particles pass througha screen or sieve with openings of the particle size or larger. Forexample, particles with a maximum size of 100 micrometers or less wouldpass through a screen or sieve with openings that are 100 micrometersacross. In another manner of characterizing particle size in connectionwith the particle-loaded polymeric fibers of the present invention, themaximum size may be described as a function of the fiber diameter. Forexample, it may be preferred that the maximum size of the particles in aparticulate-loaded fiber of the present invention be 10% or less of thefiber diameter, 30% or less of the fiber diameter, or 50% or less of thefiber diameter.

The particulate-loaded fibers of the present invention may preferably bemanufactured by methods that involve the extrusion of a polymer meltstream from a die having one or more orifices. The particles to beencapsulated within the body of the fiber are preferably entrainedwithin the polymer melt stream as it is delivered to the die.

A lubricant is delivered to the die separately from the polymer meltstream, preferably in a manner that results in the lubricant beingpreferentially located about the outer surface of the polymer meltstream as it passes through the die. The lubricant may be anotherpolymer or another material such as, e.g., mineral oil, etc. It may bepreferred that the viscosity of the lubricant be substantially less thanthe viscosity of the lubricated polymer (under the conditions at whichthe lubricated polymer is extruded). Some exemplary dies and fibers thatmay be extruded from them are described below.

One potential advantage of using a lubricant in the methods and systemsof the present invention is that the process window at which fibers maybe manufactured may be widened relative to conventional polymer fiberextrusion processes. FIG. 2 depicts a dimensionless graph to illustratethis potential advantage. The flow rate of the polymer melt streamincreases moving to the right along the x-axis and the flow rate of thelubricant increases moving upward along the y-axis. The area between thebroken line (depicted nearest the x-axis) and the solid line (locatedabove the broken line) is indicative of area in which the flow rates ofthe polymer melt stream and the lubricant can be maintained at a steadystate with respect to each other. Characteristics of steady state floware preferably steady pressures for both the polymer melt stream and thelubricant. In addition, steady state flow may also preferably occur atrelatively low pressures for the lubricant and/or the polymer meltstream.

The area above the solid line (on the opposite side of the solid linefrom the broken line) is indicative of the region in which an excess oflubricant may cause flow of the polymer melt stream through the die topulse. In some instances, the pulsation can be strong enough tointerrupt the polymer melt stream flow and break or terminate any fibersexiting the die.

The area below the broken line (i.e., between the broken line and thex-axis) is indicative of the conditions at which the lubricant flowstalls or moves to zero. In such a situation, the flow of the polymermelt stream is no longer lubricated and the pressure of the polymer meltstream and the lubricant typically rise rapidly. For example, thepressure of the polymer melt stream can rise from 200 psi (1.3×10⁶ Pa)to 2400 psi (1.4×10⁷ Pa) in a matter of seconds under such conditions.This area would be considered the conventional operating window fortraditional non-lubricated fiber forming dies, with the mass flow rateof the polymers being limited principally by the high operatingpressures.

The widened process window illustrated in FIG. 2 may preferably beprovided using a die in which the orifices converge in a manner thatresults in essentially pure elongational flow of the polymer. To do so,it may be preferred that the die orifice have a semi-hyperbolicconverging profile along its length (i.e., the direction in which thefirst polymer flows) as discussed herein.

Among the potential advantages of at least some embodiments of thepresent invention is the ability to manufacture polymeric fibers ofpolymeric materials that are not typically extruded into polymericfibers. Melt flow index is a common industry term related to the meltviscosity of a polymer. American Society for Testing and Materials(ASTM) includes a test method (ASTM D1238). This test method specifiesloads and temperatures that are to be used to measure specific polymertypes. As used herein, melt flow index values are to be obtained at theconditions specified by ASTM D1238 for the given polymer type. Thegeneral principle of melt index testing involves heating the polymer tobe tested in a cylinder with a plunger on top and a small capillary ororifice located at the bottom of the cylinder. When thermallyequilibrated, a predetermined weight is placed on the plunger andextrudate is collected and weighed for a predetermined amount of time. Ahigher melt index value is typically associated with a higher flow rateand lower viscosity, both of which may be indicative of a lowermolecular weight. Conversely, low melt index values are typicallyassociated with lower flow rates and higher viscosities, both of whichmay be indicative of a higher molecular weight polymer.

In conventional polymeric fiber extrusion processes, the MFI of theextruded polymers is about 35 or higher. Using the methods of thepresent invention, the polymer melt stream used to form the extrudedpolymeric fibers may include one or more polymers, with all of the oneor more polymers exhibiting a MFI of 30 or less, in some instances 10 orless, in other instances 1 or less, and in still other instances 0.1 orless. In some embodiments, the polymer melt stream may consistessentially of one polymer that preferably exhibits a MFI of 30 or less,in some instances 10 or less, in other instances 1 or less, and in stillother instances 0.1 or less.

In some embodiments, the polymer melt stream may be characterized asincluding a bulk polymer that forms at least a majority of the volume ofthe polymer melt stream. In some instances, it may be preferred that thebulk polymer form 60% or more of the volume of the polymer melt stream,or in other instances, it may be preferred that the bulk polymer form75% or more of the volume of the polymer melt stream. In theseinstances, the volumes are determined as the polymer melt stream isdelivered to the orifice of a die.

The bulk polymer may preferably exhibit a MFI of 30 or less, in someinstances 10 or less, in other instances 1 or less, and in still otherinstances 0.1 or less. In embodiments that can be characterized asincluding a bulk polymer, the polymer melt stream may include one ormore secondary polymers in addition to the bulk polymer. In variousembodiments, the secondary polymers may preferably exhibit a MFI of 30or less, in some instances 10 or less, in other instances 1 or less, andin still other instances 0.1 or less.

Some examples of polymers that may be low MFI polymers and that may beextruded into fibers in connection with the present invention mayinclude, e.g., Ultra High Molecular Weight polyethylene (UHMWPE),Ethylene-Propylene-Diene-Monomer (EPDM) rubber, high molecular weightpolypropylene, polycarbonate, ABS, AES, polyimids, norbornenes, Z/N andMetallocene copolymers (EAA, EMAA, EMMA, etc), polyphenylene sulfide,ionomers, polyesters, polyamides, and derivatives (e.g., PPS, PPO PPE).

Other examples of low MFI polymers that may be compatible with thepresent invention are the traditional “glassy” polymers. The term“glassy” used here is the same traditional use of a dense randommorphology that displays a glass transition temperature (T_(g)),characteristic of density, rheology, optical, and dielectric changes inthe material. Examples of glassy polymers may include, but are notlimited to: polymethylmethacrylates, polystyrenes, polycarbonates,polyvinylchlorides, etc.

Still other examples of low MFI polymers that may be compatible with thepresent invention are the traditional “rubbery” polymers. The term“rubbery” is the same as used in traditional nomenclature: a randommacromolecular material with sufficient molecular weight to formsignificant entanglement so as to result in a material with a longrelaxation time. Examples of “rubbery” polymers may include, but are notlimited to; polyurethanes, ultra low density polyethylenes, styrenicblock copolymers such as styrene-isoprene-styrene (SIS),styrene-butadiene-styrene (SBS) styrene-ethylene/butylene-styrene(SEBS), polyisoprenes, polybutadienes, EPDM rubber, and their analogues.

For those polymers that are not typically characterized by MFI, analternative may be found in melt viscosity. While MFI is inverselyrelated to molecular weight, melt viscosity typically increases withincreasing molecular weight of the selected polymer. Examples ofpolymers that may more typically be characterized by melt viscosityinclude, e.g., polyesters, polyamides (e.g., nylons), etc. As usedherein, melt viscosity for a given polymer is measured at thetemperature at which the polymer is delivered to the entrance of the dieorifice. It may be preferred that, for polymers characterized by meltviscosity, the melt viscosity of the polymers used in connection withthe present invention be about 100 Pascal-seconds (Pa·s) or higher. Thepresent invention may also be used to melt extrude fibers using polymerswith melt viscosity of 200 Pascal-seconds or higher, 300 Pascal-secondsor higher, or 400 Pascal-seconds or higher.

The present invention may also be used to extrude amorphous polymersinto fibers. As used herein, an “amorphous polymer” is a polymer havinglittle to no crystallinity usually indicated by the lack of adistinctive melting point or first order transition when heated in adifferential scanning calorimeter according to ASTM D3418.

In still other embodiments, a potential advantage of the presentinvention may be found in the ability to extrude polymeric fibers usinga multiphase polymer as the polymer melt stream and a lubricant. Bymultiphase polymer, we may mean, e.g., organic macromolecules that arecomposed of different species that coalesce into their own separateregions. Each of the regions has its own distinct properties such asglass transition temperature (Tg), gravimetric density, optical density,etc. One such property of a multiphase polymer is one in which theseparate polymeric phases exhibit different theological responses totemperature. More specifically, their melt viscosities at extrusionprocess temperatures can be distinctly different. Examples of somemultiphase polymers may be disclosed in, e.g., U.S. Pat. Nos. 4,444,841(Wheeler), 4,202,948 (Peascoe), and 5,306,548 (Zabrocki et al.).

As used herein, “multiphase” refers to an arrangement of macromoleculesincluding copolymers of immiscible monomers. Due to the incompatibilityof the copolymers present, distinctly different phases or “domains” maybe present in the same mass of material. Examples of thermoplasticpolymers that may be suitable for use in extruding multiphase polymerfibers according to the present invention include, but are not limitedto materials from the following classes: multiphase polymers ofpolyethers, polyesters, or polyamides; oriented syndiotacticpolystyrene, polymers of ethylene-propylene-diene monomers (“EPDM”),including ethylene-propylene-nonconjugated diene ternary copolymersgrafted with a mixture of styrene and acrylonitrile (also known asacrylonitrile EPDM styrene or “AES”); styrene-acrylonitrile (“SAN”)copolymers including graft rubber compositions such as those comprisinga crosslinked acrylate rubber substrate (e.g., butyl acrylate) graftedwith styrene and acrylonitrile or derivatives thereof (e.g.,alpha-methyl styrene and methacrylonitrile) known as “ASA” oracrylate-styrene-acrylonitrile copolymers, and those comprising asubstrate of butadiene or copolymers of butadiene and styrene oracrylonitrile grafted with styrene or acrylonitrile or derivativesthereof (e.g., alpha-methyl styrene and methacrylonitrile) known as“ABS” or acrylonitrile-butadiene-styrene copolymers, as well asextractable styrene-acrylonitrile copolymers (i.e., nongraft copolymers)also typically referred to as “ABS” polymers; and combinations or blendsthereof. As used herein, the term “copolymer” should be understood asincluding terpolymers, tetrapolymers, etc.

Some examples of polymers that may be used in extruding multiphasepolymer fibers may be found within the styrenic family of multiphasecopolymer resins (i.e., a multiphase styrenic thermoplastic copolymer)referred to above as AES, ASA, and ABS, and combinations or blendsthereof. Such polymers are disclosed in U.S. Pat. Nos. 4,444,841(Wheeler), 4,202,948 (Peascoe), and 5,306,548 (Zabrocki et al.). Theblends may be in the form of multilayered fibers where each layer is adifferent resin, or physical blends of the polymers which are thenextruded into a single fiber. For example, ASA and/or AES resins can becoextruded over ABS.

Multiphase polymer systems can present major challenges in fiberprocessing because the different phases can have very differentrheological responses to processing. For example, the result may be poortensile response of multiphase polymers. The different rheologicalresponse of the different phases may cause wide variations in thedrawing responses during conventional fiber forming processes thatinvolve drawing or pulling of the extruded fibers. In many instances,the presence of multiple polymer phases exhibits insufficient cohesionto resist the tensile stresses of the drawing process, causing thefibers to break or rupture.

In the present invention, the unique challenges that may be associatedwith extruding multiphase polymers may be addressed based on how thematerial is oriented during fiber formation. It may be preferred that,in connection with the present invention, the multiphase polymermaterial is squeezed or ‘pushed’ through the die orifice to orient thepolymer materials (as opposed to pulling or drawing). As a result, thepresent invention may substantially reduce the potential for fracture.

Some multiphase polymers that may be used in the methods according tothe present invention are the multiphase AES and ASA resins, andcombinations or blends thereof. Commercially available AES and ASAresins, or combinations thereof, include, for example, those availableunder the trade designations ROVEL from Dow Chemical Company, Midland,Mich., and LORAN S 757 and 797 from BASF Aktiengesellschaft,Ludwigshafen, Fed. Rep. of Germany), CENTREX 833 and 401 from BayerPlastics, Springfield, Conn., GELOY from General Electric Company,Selkirk, N.Y., VITAX from Hitachi Chemical Company, Tokyo, Japan. It isbelieved that some commercially available AES and/or ASA materials alsohave ABS blended therein. Commercially available SAN resins includethose available under the trade designation TYRIL from Dow Chemical,Midland, Mich. Commercially available ABS resins include those availableunder the trade designation CYOLAC such as CYOLAC GPX 3800 from GeneralElectric, Pittsfield, Mass.

The multiphase polymer fibers can also be prepared from a blend of oneor more of the above-listed materials and one or more otherthermoplastic polymers. Examples of such thermoplastic polymers that canbe blended with the above-listed yielding materials include, but are notlimited to, materials from the following classes: biaxially orientedpolyethers; biaxially oriented polyesters; biaxially orientedpolyamides; acrylic polymers such as poly(methyl methacrylate);polycarbonates; polyimides; cellulosics such as cellulose acetate,cellulose (acetate-co-butyrate), cellulose nitrate; polyesters such aspoly(butylene terephthalate), poly(ethylene terephthalate);fluoropolymers such as poly(chlorofluoroethylene), poly(vinylidenefluoride); polyamides such as poly(caprolactam), poly(amino caproicacid), poly(hexamethylene diamine-co-adipic acid), poly(amide-co-imide),and poly(ester-co-imide); polyetherketones; poly(etherimide);polyolefins such as poly(methylpentene); aliphatic and aromaticpolyurethanes; poly(phenylene ether); poly(phenylene sulfide); atacticpoly(styrene); cast syndiotactic polystyrene; polysulfone; siliconemodified polymers (i.e., polymers that contain a small weight percent(less than 10 weight percent) of silicone) such as silicone polyamideand silicone polycarbonate; ionomeric ethylene copolymers such aspoly(ethylene-co-methacrylic acid) with sodium or zinc ions, which areavailable under the trade designations SURLYN-8920 and SURLYN-9910 fromE.I. duPont de Nemours, Wilmington, Del.; acid functional polyethylenecopolymers such as poly(ethylene-co-acrylic acid) andpoly(ethylene-co-methacrylic acid), poly(ethylene-co-maleic acid), andpoly(ethylene-co-fumaric acid); fluorine modified polymers such asperfluoropoly(ethyleneterephthalate); and mixtures of the above polymerssuch as a polyimide and acrylic polymer blend, and apoly(methylmethacrylate) and fluoropolymer blend.

The polymer compositions used in connection with the present inventionmay include other ingredients, e.g., UV stabilizers and antioxidantssuch as those available from Ciba-Geigy Corp., Ardsley, N.Y., under thetrade designation IRGANOX, pigments, fire retardants, antistatic agents,mold release agents such as fatty acid esters available under the tradedesignations LOXIL G-715 or LOXIL G-40 from Henkel Corp., Hoboken, N.J.,or WAX E from Hoechst Celanese Corp., Charlotte, N.C. Colorants, such aspigments and dyes, can also be incorporated into the polymercompositions. Examples of colorants may include rutile TiO₂ pigmentavailable under the trade designation R960 from DuPont de Nemours,Wilmington, Del., iron oxide pigments, carbon black, cadmium sulfide,and copper phthalocyanine. Often, the above-identified polymers arecommercially available with one or more of these additives, particularlypigments and stabilizers. Typically, such additives are used in amountsto impart desired characteristics. Preferably, they are used in amountsof about 0.02-20 wt-%, and more preferably about 0.2-10 wt-%, based onthe total weight of the polymer composition.

Another potential advantage of at least some embodiments of the presentinvention is the ability to extrude the polymer melt stream at arelatively low temperature. For example, in the case of semi-crystallinepolymers, it may be possible to extrude the polymer melt stream when theaverage temperature of the polymer melt stream as pushed through theentrance of each orifice in the die is within 10 degrees Celsius or lessabove a melt processing temperature of the polymer melt stream. In someembodiments, the average temperature of the polymer melt stream maypreferably be at or below a melt processing temperature of the polymermelt stream before the polymer melt stream leaves the exit of theorifice. To do so, it may be preferred that the die temperature becontrolled to a temperature that is at or below the melt processingtemperature of the polymer melt stream.

Although not wishing to be bound by theory, it is theorized that thepresent invention may rely on the dominance of the lubricant propertiesto process the polymer during extrusion, with the polymer viscosityplaying a relatively minor factor in stress (pressure and temperature)response. Further, the presence of the lubricant may allow “quenching”(e.g., crystal or glass “vitrification” formation) of the polymer withinthe die. A potential advantage of in-die quenching may include, e.g.,retaining orientation and dimensional precision of the extrudate.

As used herein, the “melt processing temperature” of the polymer meltstream is the lowest temperature at which the polymer melt stream iscapable of passing through the orifices of the die within a period of 1second or less. In some instances, the melt processing temperature maybe at or slightly above the glass transition temperature if the polymermelt stream is amorphous or at or slightly above the melting temperatureif the polymer melt stream is crystalline or semicrystalline. If thepolymer melt stream includes one or more amorphous polymers blended witheither or both of one or more crystalline and one or moresemicrystalline polymers, then the melt processing temperature is thelower of the lowest glass transition temperature of the amorphouspolymers or the lowest melting temperature of the crystalline andsemicrystalline polymers.

One exemplary die orifice that may be used in dies according to thepresent invention is depicted in the cross-sectional view of FIG. 3 inwhich a die plate 10 and a complementary die plate cover 12 are depictedin a cross-sectional view. The die plate 10 and die plate cover 12define a polymer delivery passage 20 that is in fluid communication withan orifice 22 in the die plate 10. The portion of the polymer deliverypassage 20 formed in the die plate cover 12 terminates at opening 16,where the polymer melt stream enters the portion of polymer deliverypassage 20 formed within the die plate 10 through opening 14. In thedepicted embodiment, the opening 16 in the die plate cover 12 isgenerally the same size as the opening 14 in the die plate 10.

FIG. 4 depicts an enlarged view of the orifice 22 with the addition ofreference letter “r” indicative of the radius of the orifice 22 and “z”indicative of the length of the orifice 22 along the axis 11. Theorifice 22 formed in the die plate 10 may preferably converge such thatthe cross-sectional area (measured transverse to the axis 11) is smallerthan the cross-sectional area of the entrance 24. It may be preferredthat, as discussed herein, the shape of the die orifice 22 be designedsuch that the elongational strain rate of the polymer melt stream beconstant along the length of the orifice 22 (i.e., along axis 11).

As discussed herein, it may be preferred that the die orifice have aconverging semi-hyperbolic profile. The definition of a“semi-hyperbolic” shape begins with the fundamental relationship betweenvolume flow, area of channel and fluid velocity. Although cylindricalcoordinates are used in connection with the description of orifice 22,it should be understood that die orifices used in connection with thepresent invention may not have a circular cylindrical profile.

Flow through the orifice 22 along axis 11 can be described at eachposition along the axis 11 by the following equation:

Q=V*A  (1)

where Q is the measure of volumetric flow through the orifice, V is theflow velocity through the orifice, and A is the cross-sectional area ofthe orifice 22 at the selected location along the axis 11.

Equation (1) can be rearranged and solved for velocity to yield thefollowing equation:

V=Q/A  (2)

Because the cross-sectional area of a converging orifice changes alongthe length of the channel of the orifice, the following equation can beused to describe the various relationships between variables in Equation(2):

dV _(z) /dz=(−Q/A ²)(dA/dz)  (3)

In Equation (3), the expression for the change in velocity with thechange in position down the length of the orifice also definesextensional flow (O) of the fluid. Steady or constant extensional flowmay be a preferred result of flow through a converging orifice. As aresult, it may be preferred that the cross-sectional area of the orificechange in such a way as to result in constant extensional flow throughthe orifice. An equation that defines steady or constant extensionalflow may be expressed as:

dV _(z) /dz=ε=constant  (4)

An expression that can be substituted for the change in area with thechange in position down the length of the orifice and that will yield aconstant or steady extensional flow may be expressed as

f(r,z)=Constant=r ² z  (5)

A generic form of the expression of Equation (5) may be the following:

f(r,z)=C ₁ +C ₂ r ² z  (6)

Equation (6) may be used to determine the shape of an orifice 22 as usedin connection with the present invention. To design the shape of anorifice, it may be preferred that the geometric constraint of thediameter of the exit 26 of the orifice 22 be determined (with theunderstanding that exit diameter is indicative of the fiber sizeextruded from the orifice 22). Alternatively, the diameter of theentrance 24 of the orifice 22 may be used.

When the radius (and, thus, the corresponding area) of one of entrance24 or the exit 26 of the orifice 22 is chosen, then the other may bedetermined by selecting the desired extensional strain selected, thenthe other radius (i.e., the radius of the entrance 24 or the exit 26)may preferably be determined by selecting the desired extensional strainto experienced by the fluid (i.e., polymer melt stream) passing throughthe orifice 22.

This value, i.e., the extensional strain, may sometimes be referred toas the “Hencky Strain.” Hencky Strain is based on extensional orengineering strain of a material being stretched. The equation presentedbelow describes Hencky Strain for a fluid in passing through a channel,e.g., an orifice in the present invention:

Hencky Strain on Fluid=ln(r _(o) ² /r _(z) ²)=ln(A _(o) /A _(z)).  (7)

Selection of the desired Hencky Strain to be experienced by the fluidpassing through the orifice fixes or sets the radius (and, thus, thearea) the other end of the orifice as discussed above. The lastremaining design feature is to establish the length of the orifice to belubricated. Once the length of the orifice 22 (“z” in FIG. 4) isselected and the radii/areas of the entrance 24 and exit are known,Equation 6 can be regressed for radius (area) change with the change inposition down the length of the orifice 22 (along the “z” direction) toobtain the constants C₁ and C₂. The following equation provides theradius of the orifice at each location along the “z” dimension (r_(z)):

r _(z)=[((z)(e ^(s)−1)+Length)/(r _(entrance) ²*Length)]^(−1/2)  (8)

where z is the location along the longitudinal axis in the z directionas measured from the entrance of the orifice;e=(r_(entrance))²/(r_(exit))²; s=Hencky Strain; r_(entrance) is theradius at the entrance to the orifice; r_(exit) is the radius at theexit of the orifice; and Length is the overall length of the orifice inthe z direction from the entrance to the exit of the orifice. For adiscussion of Hencky Strain and associated principles, reference may behad to C. W. Macosko “Rheology—Principles, Measurements andApplications,” pp. 285-336 (Wiley-VCH Inc., New York, 1^(st) Ed. 1994).

Returning to FIG. 3, the die plate 10 also includes a lubricant passage30 in fluid communication with a lubricant plenum 32 formed between thedie plate 10 and the die plate cover 12. The die plate 10 and the dieplate cover 12 preferably define a gap 34 such that a lubricant passedinto the lubricant plenum 32 through the lubricant passage 30 will passinto the polymer delivery passage 20 from slot 36 and through opening14. As such, the lubricant can be delivered to the orifice 22 separatelyfrom the polymer melt stream.

The slot 36 may preferably extend about the perimeter of the polymerdelivery passage 20. The slot 36 may preferably be continuous ordiscontinuous about the perimeter of the polymer delivery passage 20.The spacing between the die plate 10 and the die plate cover 12 thatforms gap 34 and slot 36 may be adjusted based on a variety of factorssuch as the pressure at which a polymer melt stream is passed throughthe polymer delivery passage 20, the relative viscosities of the polymermelt stream and the lubricant, etc. In some instances, the slot 36 maybe in the form of an opening or openings formed by the interface of tworoughened (e.g., sandblasted, abraded, etc.) surfaces forming gap 34 (orone roughened surface and an opposing smooth surface).

FIG. 5 is a plan view of the die plate 10 with the die plate cover 12removed. Multiple openings 14, polymer delivery passages 20, dieorifices 22, and lubricant plenums 32 are depicted therein. The depictedpolymer delivery passages 20 have a constant cross-sectional area(measured transverse to the axis 11 in FIG. 3) and are, in the depictedembodiment, circular cylinders. It should be understood, however, thatthe polymer delivery passages 20 and associated die orifices 22 may haveany suitable cross-sectional shape, e.g., rectangular, oval, elliptical,triangular, square, etc.

It may be preferred that the lubricant plenums 32 extend about theperimeters of the polymer delivery passages 20 as seen in FIG. 5 suchthat the lubricant can be delivered about the perimeter of the polymerdelivery passages 20. By doing so, the lubricant preferably forms alayer about the perimeter of a polymer melt stream as it passes throughthe polymer delivery passages 20 and into the die orifices 22. In thedepicted embodiment, the plenums 32 are supplied by lubricant passages30 that extend to the outer edges of the die plate 10 as seen in FIG. 5.

It may be preferred that each of the plenums 32 be supplied by anindependent lubricant passage 30 as seen in FIG. 5. By supplying each ofthe plenums 32 (and their associated die orifices 22) independently,control over a variety of process variable can be obtained. Thosevariables may include, for example, the lubricant pressure, thelubricant flow rate, the lubricant temperature, the lubricantcomposition (i.e., different lubricants may be supplied to differentorifices 22), etc.

As an alternative, however, it may be preferred in some systems that amaster plenum be used to supply lubricant to each of the lubricantpassages 30 which, in turn, supply lubricant to each of the plenums 32associated with the orifices 22. In such a system, the delivery oflubricant to each orifice may preferably be balanced between all of theorifices.

FIG. 6 is a schematic diagram of one system 90 that may be used inconnection with the present invention. The system 90 may preferablyinclude polymer sources 92 and 94 that deliver polymer to an extruder96. Although two polymer sources are depicted, it should be understoodthat only one polymer source may be provided in some systems. Inaddition, other systems may include three or more polymer sources.Furthermore, although only a single extruder 96 is depicted, it shouldbe understood that system 90 may include any extrusion system orapparatus capable of delivering the desired polymer or polymers to thedie 98 in accordance with the present invention.

In addition to one or more polymer sources 92 and 94, the system 90 alsoincludes a particle source 91 that, in the depicted embodiment, providesparticles to be entrained within the polymer from polymer source 92.Alternatively, the particle source 91 could input its particles into theextruder 96 (or extruders if multiple extruders are used). Regardless ofthe specific arrangement, it is preferred that the particles from theparticle source 91 be entrained within the polymer melt stream as it isdelivered to die 98.

The system 90 further includes a lubricant apparatus 97 operablyattached to the die 98 to deliver lubricant to the die in accordancewith the principles of the present invention. In some instances, thelubricant apparatus 97 may be in the form of a lubricant polymer sourceand extrusion apparatus.

Also depicted in connection with the system 90 are two fibers 40 beingextruded from the die 98. Although two fibers 40 are depicted, it shouldbe understood that only one fiber may be produced in some systems, whileother systems may produce three or more polymer fibers at the same time.

FIG. 7 depicts another exemplary embodiment of a die orifice that may beused in connection with the present invention. Only a portion of theapparatus is depicted in FIG. 7 to illustrate a potential relationshipbetween the entrance 114 of the die orifice 122 and delivery of thelubricant through gap 134 between the die plate 110 and the die platecover 112. In the depicted apparatus, the lubricant delivered separatelyfrom the polymer melt stream is introduced at the entrance 116 of theorifice 122 through gap 134. The polymer melt stream itself is deliveredto the entrance 116 of the die orifice 122 through polymer deliverypassage 120 in die plate cover 112.

Another optional relationship depicted in the exemplary apparatus ofFIG. 7 is the relative size of the entrance 114 of the die orifice 122as compared to the size of the opening 116 leading from the polymerdelivery passage 120 into the entrance 114. It may be preferred that thecross-sectional area of the opening 116 be less than the cross-sectionalarea of the entrance 114 to the die orifice 122. As used herein,“cross-sectional area” of the openings is determined in a planegenerally transverse to the longitudinal axis 111 (which is, preferably,the direction along which the polymer melt stream moves through thepolymer delivery passage and the die orifice 122).

FIG. 8 depicts yet another potential apparatus that may be used inconnection with the present invention. FIG. 8 is an enlarged plan viewof one die orifice 222 taken from above the die plate 210 (in a viewsimilar to that seen in FIG. 5). The entrance 216 to the die orifice 222is depicted along with the exit 226 of the die orifice 222. Onedifference between the design depicted in FIG. 8 and that depicted inthe previous figures is that the lubricant is delivered to the dieorifice 222 through multiple openings formed at the end of channels 234a, 234 b, and 234 c. This is in contrast to the continuous slot formedby the gap between the die plate and the die plate cover in theembodiments described above. Although three openings for deliveringlubricant are depicted, it should be understood that as few as two andmore than three such openings may be provided.

FIG. 9 depicts a flow of the polymer melt stream 40 and a lubricant 42from the exit 26 of a die in accordance with the present invention. Thepolymer melt stream 40 and lubricant 42 are shown in cross-section,depicting the lubricant 42 on the outer surface 41 of the polymer meltstream 40. It may be preferred that the lubricant be provided on theentire outer surface 41 such that the lubricant 42 is located betweenthe polymer melt stream 40 and the interior surface 23 of the dieorifice.

Although the lubricant 42 is depicted on the outer surface 41 of thepolymer melt stream 40 after the polymer melt stream 40 has left theorifice exit 26, it should be understood that, in some instances, thelubricant 42 may be removed from the outer surface 41 of the polymermelt stream 40 as or shortly after the polymer melt stream 40 andlubricant 42 leave the die exit 26.

Removal of the lubricant 42 may be either active or passive. Passiveremoval of the lubricant 42 may involve, e.g., evaporation, gravity oradsorbents. For example, in some instances, the temperature of thelubricant 42 and/or the polymer melt stream 40 may be high enough tocause the lubricant 42 to evaporate without any further actions afterleaving the die exit 26. In other instances, the lubricant may beactively removed from the polymer melt stream 40 using, e.g., a water oranother solvent, air jets, etc.

Depending on the composition of the lubricant 42, a portion of thelubricant 42 may remain on the outer surface 41 of the polymer meltstream 40. For example, in some instance the lubricant 42 may be acomposition of two or more components, such as one or more carriers andone or more other components. The carriers may be, e.g., a solvent(water, mineral oil, etc.) that are removed actively or passively,leaving the one or more other components in place on the outer surface41 of the polymer melt stream 40.

In other situations, the lubricant 42 may be retained on the outersurface 41 of the polymer melt stream 40. For example, the lubricant 42may be a polymer with a viscosity that is low enough relative to theviscosity of the polymer melt stream 40 such that it can function as alubricant during extrusion. Examples of potentially suitable polymersthat may also function as lubricants may include, e.g., polyvinylalcohols, high melt flow index polypropylenes, polyethylenes, etc.

Regardless of whether the lubricant 42 is removed from the surface 41 ofthe polymer melt stream 40 or not, the lubricant 42 may act as aquenching agent to increase the rate at which the polymer melt stream 40cools. Such a quenching effect may help to retain particular desiredstructures in the polymer melt stream 40 such as orientation within thepolymer melt stream 40. To assist in quenching, it may be desirable, forexample, to provide the lubricant 42 to the die orifice at a temperaturethat is low enough to expedite the quenching process. In otherinstances, the evaporative cooling that may be provided using somelubricants may be relied on to enhance the quenching of the polymer meltstream 40. For example, mineral oil used as a lubricant 42 may serve toquench a polypropylene fiber as it evaporates from the surface of thepolypropylene (the polymer melt stream) after exiting the die.

The present invention may preferably rely on a viscosity differencebetween the lubricant materials and the extruded polymer. Viscosityratios of polymer to lubricant of, e.g., 40:1 or higher, or 50:1 orhigher may preferably be a significant factor in selecting the lubricantto be used in connection with the methods of the present invention. Thelubricant chemistry may be secondary to its theological behavior. Inthis description, materials such as SAE 20 weight oil, white paraffinoil, and polydimethyl siloxane (PDMS) fluid are all examples ofpotentially suitable lubricant materials. The following list is notintended to be a limit on the lubricant candidates, i.e., othermaterials may be used as lubricants in connection with the presentinvention.

Non-limiting examples of inorganic or synthetic oils may include mineraloil, petrolatum, straight and branched chain hydrocarbons (andderivatives thereof), liquid paraffins and low melting solid paraffinwaxes, fatty acid esters of glycerol, polyethylene waxes, hydrocarbonwaxes, montan waxes, amide wax, glycerol monostearate. etc.

Many kinds of oils and fatty acid derivatives thereof may also besuitable lubricants in connection with the present invention. Fatty acidderivatives of oils can be used, such as, but not limited to, oleicacid, linoleic acid, and lauric acid. Substituted fatty acid derivativesof oils may also be used, such as, but not limited to, oleamide, propyloleate and oleyl alcohol (it may be preferred that the volatility ofsuch materials is not so high so as to evaporate before extrusion).Examples of some potentially suitable vegetable oils may include, butnot limited to, apricot kernel oil, avocado oil, baobab oil, blackcurrant oil, calendula officinalis oil, cannabis sativa oil, canola oil,chaulmoogra oil, coconut oil, corn oil, cottonseed oil, grape seed oil,hazelnut oil, hybrid sunflower oil, hydrogenated coconut oil,hydrogenated cottonseed oil, hydrogenated palm kernel oil, jojoba oil,kiwi seed oil, kukui nut oil, macadamia nut oil, mango seed oil,meadowfoam seed oil, mexican poppy oil, olive oil, palm kernel oil,partially hydrogenated soybean oil, peach kernel oil, peanut oil, pecanoil, pistachio nut oil, pumpkin seed oil, quinoa oil, rapeseed oil, ricebran oil, safflower oil, sasanqua oil, sea buckthorn oil, sesame oil,shea butter fruit oil, sisymbrium irio oil, soybean oil, sunflower seedoil, walnut oil, and wheat germ oil.

Other potentially suitable lubricant materials may include, e.g.,saturated aliphatic acids including hexanoic acid, caprylic acid,decanoic acid, undecanoic acid, lauric acid, myristic acid, palmiticacid and stearic acid, unsaturated aliphatic acids including oleic acidand erucic acid, aromatic acids including benzoic acid, phenyl stearicacid, polystearic acid and xylyl behenic acid and other acids includingbranched carboxylic acids of average chain lengths of 6, 9, and 11carbons, tall oil acids and rosin acid, primary saturated alcoholsincluding 1-octanol, nonyl alcohol, decyl alcohol, 1-decanol,1-dodecanol, tridecyl alcohol, cetyl alcohol and 1-heptadecanol, primaryunsaturated alcohols including undecylenyl alcohol and oleyl alcohol,secondary alcohols including 2-octanol, 2-undecanol, dinonyl carbinoland diundecyl carbinol and aromatic alcohols including 1-phenyl ethanol,1-phenyl-1-pentanol, nonyl phenyl, phenylstearyl alcohol and 1-naphthol.Other potentially useful hydroxyl-containing compounds may includepolyoxyethylene ethers of oleyl alcohol and a polypropylene glycolhaving a number average molecular weight of about 400. Still furtherpotentially useful liquids may include cyclic alcohols such as 4,t-butyl cyclohexanol and methanol, aldehydes including salicyl aldehyde,primary amines such as octylamine, tetradecylamine and hexadecylamine,secondary amines such as bis-(1-ethyl-3-methyl pentyl) amine andethoxylated amines including N-lauryl diethanolamine, N-tallowdiethanol-amine, N-stearyl diethanolamine and N-coco diethanolamine.

Additional potentially useful lubricant materials may include aromaticamines such as N-sec-butylaniline, dodecylaniline, N,N-dimethylaniline,N,N-diethylaniline, p-toluidine, N-ethyl-o-toluidine, diphenylamine andaminodiphenylmethane, diamines including N-erucyl-1,3-propane diamineand 1,8-diamino-p-methane, other amines including branched tetraminesand cyclodecylamine, amides including cocoamide, hydrogenated tallowamide, octadecylamide, eruciamide, N,N-diethyl toluamide andN-trimethylopropane stearamide, saturated aliphatic esters includingmethyl caprylate, ethyl laurate, isopropyl myristate, ethyl palmitate,isopropropyl palmitate, methyl stearate, isobutyl stearate and tridecylstearate, unsaturated esters including stearyl acrylate, butylundecylenate and butyl oleate, alkoxy esters including butoxyethylstearate and butoxyethyl oleate, aromatic esters including vinyl phenylstearate, isobutyl phenyl stearate, tridecyl phenyl stearate, methylbenzoate, ethyl benzoate, butyl benzoate, benzyl benzoate, phenyllaurate, phenyl salicylate, methyl salicylate and benzyl acetate anddiesters including dimethyl phenylene distearate, diethyl phthalate,dibutyl phthalate, di-iso-octyl phthalate, dicapryl adipate, dibutylsebacate, dihexyl sebacate, di-iso-octyl sebacate, dicapryl sebacate anddioctyl maleate. Yet other potentially useful lubricant materials mayinclude polyethylene glycol esters including polyethylene glycol (whichmay preferably have a number of average molecular weight of about 400),diphenylstearate, polyhydroxylic esters including castor oil(triglyceride), glycerol monostearate, glycerol monooleate, glycoldistearate glycerol dioleate and trimethylol propane monophenylstearate,ethers including diphenyl ether and benzyl ether, halogenated compoundsincluding hexachlorocyclopentadiene, octabromobiphenyl,decabromodiphenyl oxide and 4-bromodiphenyl ether, hydrocarbonsincluding 1-nonene, 2-nonene, 2-undecene, 2-heptadecene, 2-nonadecene,3-eicosene, 9-nonadecene, diphenylmethane, triphenylmethane andtrans-stilbene, aliphatic ketones including 2-heptanone, methyl nonylketone, 6-undecanone, methylundecyl ketone, 6-tridecanone,8-pentadecanone, 11-pentadecanone, 2-heptadecanone, 8-heptadecanone,methyl heptadecyl ketone, dinonyl ketone and distearyl ketone, aromaticketones including acetophenone and benzophenone and other ketonesincluding xanthone. Still further potentially useful lubricants mayinclude phosphorous compounds including trixylenyl phosphate,polysiloxanes, Muget hyacinth (An Merigenaebler, Inc), Terpineol PrimeNo. 1 (Givaudan-Delawanna, Inc), Bath Oil Fragrance #5864 K(International Flavor & Fragrance, Inc), Phosclere P315C(organophosphite), Phosclere P576 (organophosphite), styrenated nonylphenol, quinoline and quinalidine.

Oils with emulsifier qualities may also potentially be used as lubricantmaterials, such as, but not limited to, neatsfoot oil, neem seed oil,PEG-5 hydrogenated castor oil, PEG-40 hydrogenated castor oil, PEG-20hydrogenated castor oil isostearate, PEG-40 hydrogenated castor oilisostearate, PEG-40 hydrogenated castor oil laurate, PEG-50 hydrogenatedcastor oil laurate, PEG-5 hydrogenated castor oil triisostearate, PEG-20hydrogenated castor oil triisostearate, PEG-40 hydrogenated castor oiltriisostearate, PEG-50 hydrogenated castor oil triisostearate, PEG-40jojoba oil, PEG-7 olive oil, PPG-3 hydrogenated castor oil,PPG-12-PEG-65 lanolin oil, hydrogenated mink oil, hydrogenated oliveoil, lanolin oil, maleated soybean oil, musk rose oil, cashew nut oil,castor oil, dog rose hips oil, emu oil, evening primrose oil, and goldof pleasure oil.

Test Methods Modulus:

The moduli of the fibers of the invention were measured using theprocedures described in ASTM-D2653-01. 16 mm diameter roller grips (MTS100-034-764) were used with a 14 cm grip separation and a crossheadspeed of 25.4 cm/min. A 500 N load cell was used. The diameters of thefibers were measured using an Ono Sokki thickness gauge. 5 replicateswere run and averaged.

Mass Flow Rate:

The mass flow rate was measured by a basic gravimetric method. Theexiting extrudate was captured in a pre-weighed aluminum tray for aperiod of 80 seconds. The difference between the total weight and theweight of the tray was measured in grams or kilograms.

Melt Flow Index (MFI):

The melt flow indices of the polymers were measured according to ASTMD1238 at the conditions specified for the given polymer type.

EXAMPLES

The following non-limiting examples are provided to illustrate theprinciples of the present invention.

Example 1

A polymeric fiber was produced using apparatus similar to that shown inFIG. 6. A single orifice die as shown in FIG. 7 was used. The dieorifice was circular and had an entrance diameter of 1.68 mm, an exitdiameter of 0.76 mm, a length of 12.7 mm and a semi-hyperbolic shapedefined by the equation:

r _(z)=[0.00140625/((0.625*z)+0.0625)]̂0.5  (9)

where z is the location along the axis of the orifice as measured fromthe entrance and r_(z) is the radius at location z.

Polypropylene homopolymer (FINAPRO 5660, 9.0 MFI, Atofina PetrochemicalCo., Houston, Tex.) was extruded with a 3.175 cm single screw extruder(30:1 L/D) using a barrel temperature profile of 177° C.-232° C.-246° C.and an in-line ZENITH gear pump (1.6 cubic centimeters/revolution(cc/rev)) set at 19.1 RPM. The die temperature and melt temperature wereapproximately 220° C. Chevron SUPERLA white mineral oil #31 as alubricant was supplied to the entrance of the die using a second ZENITHgear pump (0.16 cc/rev) set at 30 RPM.

The molten polymer pressure and corresponding mass flow rate of theextrudate are shown in Table 1 below. The pressure transducer for thepolymer was located in the feed block just above the die at the pointwhere the polymer was introduced to the die. The lubricant pressuretransducer was located in the lubricant delivery feed line prior tointroduction to the die. A control sample was also run without the useof lubricant.

Example 2

A polymeric fiber was produced as in Example 1 except that a die similarto that depicted in FIG. 3 was used. The die orifice had a circularprofile with an entrance diameter of 6.35 mm, an exit diameter of 0.76mm, a length of 10.16 mm and a semi-hyperbolic shape defined by Equation(8) as described herein.

Molten polymer pressure and mass flow rate of the extrudate are shown inTable 1 below with and without lubricant.

Example 3

A polymeric fiber was produced as in Example 1 except that a die asshown in FIG. 2 was used. The die orifice had a circular profile with anentrance diameter of 6.35 mm, an exit diameter of 0.51 mm, a length of12.7 mm and a semi-hyperbolic shape defined by Equation (8).

Polyurethane (PS440-200 Huntsman Chemical, Salt Lake City, Utah) wasused to form the fiber. The polymer was delivered with a 3.81 cm singlescrew extruder (30:1 L/D) using a barrel temperature profile of 177°C.-232° C.-246° C. and an in-line ZENITH gear pump (1.6 cc/rev) set at19.1 RPM. The die temperature and melt temperature was approximately215° C. Chevron SUPERLA white mineral oil #31 as a lubricant wassupplied to the entrance of the die via two gear pumps in series drivenat 99 RPM and 77 RPM respectively. Molten polymer pressure and mass flowrate of the extrudate is shown in Table 1 below. A control sample wasalso run without the use of lubricant.

Mass Flow Rates for Examples 1-3:

TABLE 1 Melt Mass Flow Pressure Rate Example (kg/cm²) (grams/min) 18.8–17.6 33.9 Control w/o lub. 8.8–17.6 4.1 2 6.3–8.4  106 Control w/olub. 52.8 94 3 5.3 45 Control w/o lub. 114 22.7Table 1 shows that at similar melt pressures, substantially higher massflow rates may be obtained using the invention process (Example 1), andat similar mass flow rates, polymer may be extruded at significantlylower pressures (Example 2). As seen in Example 3, melt pressure may besignificantly reduced and mass flow rate substantially increasedsimultaneously when using the invention process.

Example 4

A polymeric fiber was produced using the die of Example 1. Highmolecular weight polyethylene (Type 9640, 0.2 MI, Chevron PhillipsChemical Co., Houston, Tex.) was extruded with a 38 mm single screwextruder (30:1 L/D, 9 RPM) using a barrel temperature profile of 177°C.-200° C.-218° C. and an in-line ZENITH gear pump (1.6 cubiccentimeters/revolution (cc/rev)) set at 3.7 RPM. The die temperature andmelt temperature were approximately 218° C. Chevron SUPERLA whitemineral oil #31 (Chevron USA Inc., Houston, Tex.) as a lubricant wassupplied to the entrance of the die using a ZENITH dual gear single feedgear pump (0.16 cc/rev) set at 80 RPM. The extruded fiber was collectedat the die exit manually and coiled by hand.

The molten polymer pressure varied between 241 N/cm² (350 lbs/in²) and550 N/cm² (798 lbs/in²) at a mass flow rate of 2.0-2.5 kg/hr (4.5-5.5lbs/hr). The pressure transducer for the polymer was located in the feedblock just above the die at the point where the polymer was introducedto the die. The lubricant pressure transducer was located in thelubricant delivery feed line prior to introduction to the die.

Example 5

A polymeric fiber was produced as in Example 1. The die orifice had acircular profile with an entrance diameter of 6.35 mm, an exit diameterof 0.76 mm, a length of 127 mm and a semi-hyperbolic shape defined byEquation (8) as described herein. A high molecular weight fractionalmelt index polyethylene (HD7960.13, 0.06 MI, ExxonMobil Chemical Inc.,Houston, Tex.) was extruded using a 19 mm single screw (30:1 L/D, 12RPM) extruder using a barrel temperature profile of 270° C.-255° C.-240°C. fitted with a 0.16 cubic centimeters per revolution (0.16 cc/rev)gear pump operating at 6 RPM. The die temperature and melt temperaturewere approximately 218° C. Chevron SUPERLA white mineral oil #31(Chevron USA Inc., Houston, Tex.) as a lubricant was supplied to theentrance of the die using a Lorimer “air over oil” pneumatic highpressure pump (H. Lorimer Corp., Longview, Tex.).

The extruded fiber was then quenched in a water bath (approximately 20°C.) positioned approximately 5 cm beneath the die exit at a rate of 15meter/min. The fiber was then length oriented in-line between two pullrolls by immersing the fiber in a hot water bath (79° C.) with a drawratio between the two pull rolls of approximately 9:1. The orientedfiber was then run over a heated platen set at 177° C. to relax (heatset) the fiber and then wound onto a core.

The average fiber diameter was 0.305 mm. The modulus of the fiber wasmeasured to be 205 kN/cm² with a break tensile force of 46 kN.

Example 6

A polymeric fiber was produced as in Example 1 except a high molecularweight elastomeric polyethylene (ENGAGE 8100, 1.0 MI, Dow Chemical Co.,Midland, Mich.) was used to form the fiber. The polymer was deliveredwith a 38 mm single screw extruder (32:1 L/D, 14 RPM) using a barreltemperature profile of 177° C.-200° C.-2180C and an in-line ZENITH gearpump (1.6 cc/rev) set at 8 RPM resulting in a polymer flow rate ofapproximately 2.4 kg/hr. The die temperature and melt temperature wasapproximately 218° C. Chevron SUPERLA white mineral oil #31 as alubricant was supplied to the entrance of the die using a ZENITH dualgear single feed gear pump (0.16 cc/rev) set at 75 RPM. The extrudedfiber was collected at the die exit manually and coiled by hand.

Example 7

A polymeric fiber was produced as in Example 1 except an amorphousglassy polycarbonate (MACROLON 2407, Bayer Chemical Co., Leverkusen,Germany) was used to form the fiber. The polymer was delivered with a 38mm single screw extruder (32:1 L/D, 14 RPM) using a barrel temperatureprofile of 177° C.-200° C.-2290C and an in-line ZENITH gear pump (1.6cc/rev) set at 8 RPM resulting in a polymer flow rate of approximately2.4 kg/hr. The die temperature and melt temperature was approximately229° C. Chevron SUPERLA white mineral oil #31 as a lubricant wassupplied to the entrance of the die using a ZENITH dual gear single feedgear pump (0.16 cc/rev) set at 75 RPM. The extruded fiber was collectedat the die exit manually and coiled by hand.

Example 8

A polymeric fiber was produced as in Example 5 except that a nylon-6polyamide (ULTRAMID B4, BASF Corp., Wyandotte, Mich.) was extruded usinga 19 mm single screw (30:1 L/D, 18 RPM) extruder using a barreltemperature profile of 250° C.-300° C.-300° C. fitted with a 0.16 cubiccentimeters per revolution (0.16 cc/rev) gear pump operating at 8 RPM.The die temperature and melt temperature were approximately 260° C.Chevron SUPERLA white mineral oil #31 (Chevron USA Inc., Houston, Tex.)as a lubricant was supplied to the entrance of the die using a Lorimer“air over oil” pneumatic high pressure pump (H. Lorimer Corp., Longview,Tex.). A 3 mm diameter (ID) copper tubing was used to supply thelubricant from the pump to the die. The tubing was wrapped 2.5 timesaround the 7.6 cm diameter die prior to the entry port into the die.This was done to heat the temperature of the lubricant up to that of thedie.

The extruded fiber with a diameter of approximately 1 millimeter wasthen quenched in a water bath (approximately 20° C.) positionedapproximately 2.5 cm beneath the die exit at a rate of 2.4 meter/minute.The fiber was then length oriented in-line between two pull rolls byimmersing the fiber in a hot water bath (79° C.) with a draw ratiobetween the two pull rolls of approximately 4:1. The oriented fiber wasthen run over a heated platen set at 177° C. to relax (heat set) thefiber and then over a second heated platen set at 121° C. to anneal thefiber and then wound onto a core. The modulus of the fiber was measuredto be 226 kN/cm².

Example 9

A polymeric fiber was produced as in Example 8 except that significantlylower process temperatures were used to obtain a melt temperatureslightly above the polymer melting point (230° C.) resulting insignificantly higher modulus fibers. The nylon was extruded using abarrel temperature profile of 240° C.-250° C.-240° C. The melt pump wasset at 235° C., the die feed block at 230° C. and the die at 225° C. Themodulus of the fiber was measured to be 765 kN/cm².

Example 10

A polymeric fiber was produced as in Example 1 except two extruders wereused to feed two materials to a sheath/core feedblock resulting in abicomponent coextruded fiber. Polypropylene homopolymer (FINAPRO 5660,9.0 MFI, Atofina Petrochemical Co., Houston, Tex.) was used to form thecore of the fiber. The polymer was delivered with a 25 mm single screwextruder (24:1 L/D) using a barrel temperature profile of 177° C.-200°C.-232° C. and an in-line ZENITH gear pump (1.6 cc/rev) set at 24 RPM.FINAPRO 5660 pigmented with 2% orange color concentrate (Type 66Y163,Penn Color Co., Doylestown, Pa.) was used to form the sheath of thefiber. The polymer was delivered with a 19 mm single screw extruderusing a barrel temperature profile of 177° C.-195° C.-215° C.-232° C.and an in-line ZENITH gear pump (1.6 cc/rev) set at 24 RPM. The meltpump was set at 232° C., the die feed block at 232° C. and the die at232° C. The die feed block consisted of a series of 0.5 mm thickmachined plates stacked to provide a dual feed plate die as is wellknown in the art of coextruded fibers.

The lubricant introduction manifold was attached at the bottom of theplate stack. Universal Trans Hydraulic oil (Mills Fleet Farm Inc.,Brainerd, Minn.) was used as the lubricant and was supplied to theentrance of the die using a ZENITH dual gear single feed gear pump (0.16cc/rev) set at 80 RPM. The extruded fiber was collected at the die exitmanually and coiled by hand.

Example 11

A polymeric fiber was produced as in Example 1 except a multiphaseacrylonitrile-styrene-butylacrylate polymer (CENTREX 833, Marine White,3 MFI, Bayer Corp., Leverkusen, Germany) was used to form the fiber. Thepolymer was delivered with a 38 mm single screw extruder (32:1 L/D, 14RPM) using a barrel temperature profile of 177° C.-200° C.-2180C and anin-line ZENITH gear pump (1.6 cc/rev) set at 8 RPM resulting in apolymer flow rate of approximately 2.4 kg/hr. The die temperature andmelt temperature was approximately 218° C. Chevron SUPERLA white mineraloil #31 as a lubricant was supplied to the entrance of the die using aZENITH dual gear single feed gear pump (0.16 cc/rev) set at 75 RPM. Theextruded fiber was collected at the die exit manually and coiled byhand.

Example 12

A polymeric fiber was produced as in Example 10 except a nylon 12(GRILAMID G-12, EMS Chemie AG, Switzerland) filled with 10% by weightaluminum oxide abrasive (P-2000, 400 grit, Fujimi Corp., Ltd., Chicago,Ill.) was used to form the fiber. The filled polymer was delivered witha 25 mm single screw extruder (24:1 L/D) using a barrel temperatureprofile of 260° C.-260° C.-260° C. The feedblock and die were set at260° C. Chevron SUPERLA white mineral oil #31 as a lubricant wassupplied to the entrance of the die using a ZENITH dual gear single feedgear pump (0.16 cc/rev) set at 80 RPM. The extruded fiber was collectedat the die exit manually and coiled by hand. The outer surface of thefiber was very rough with a large amount of abrasive at or near theouter surface of the fiber.

As used herein and in the appended claims, the singular forms “a,”“and,” and “the” include plural referents unless the context clearlydictates otherwise. Thus, for example, reference to “a fiber” mayinclude a plurality of fibers and reference to “the orifice” mayencompass one or more orifices and equivalents thereof known to thoseskilled in the art.

All references and publications cited herein are expressly incorporatedherein by reference in their entirety into this disclosure. Illustrativeembodiments of this invention are discussed and reference has been madeto possible variations within the scope of this invention. These andother variations and modifications in the invention will be apparent tothose skilled in the art without departing from the scope of theinvention, and it should be understood that this invention is notlimited to the illustrative embodiments set forth herein. Accordingly,the invention is to be limited only by the claims provided below andequivalents thereof.

1. A particulate-loaded polymeric fiber comprising a fiber body thatcomprises a polymeric binder and a plurality of particles encapsulatedwithin the polymeric binder, wherein the polymeric binder consistsessentially of one or more polymers, and wherein the encapsulatedparticles comprise an encapsulated particle density, and wherein theencapsulated particle density is higher proximate an outer surface ofthe fiber.
 2. A fiber according to claim 1, wherein the encapsulatedparticle density within the outermost 20% of the volume of the fiber istwo times or more the encapsulated particle density within the innermost20% of the volume of the fiber.
 3. A fiber according to claim 1, whereinthe plurality of particles consist essentially of non-polymericparticles.
 4. A fiber according to claim 1, wherein the plurality ofparticles have a maximum size of 100 micrometers or less.
 5. A fiberaccording to claim 1, wherein all of the one or more polymers comprise amelt flow index of 30 or less measured at the conditions specified forthe one or more polymers.
 6. A fiber according to claim 1, wherein allof the one or more polymers comprise a melt flow index of 10 or lessmeasured at the conditions specified for the one or more polymers.
 7. Afiber according to claim 1, wherein all of the one or more polymerscomprise a melt flow index of 1 or less measured at the conditionsspecified for the one or more polymers.
 8. A fiber according to claim 1,wherein all of the one or more polymers comprise a melt flow index of0.1 or less measured at the conditions specified for the polymers.
 9. Afiber according to claim 1, wherein the one or more polymers aresemi-crystalline polymers.
 10. A fiber according to claim 9, wherein thesemi-crystalline polymers are nylon.
 11. A particulate-loaded polymericfiber comprising: a fiber body comprising one or more polymers, andwherein all of the one or more polymers comprise a melt flow index of 10or less measured at the conditions specified for the one or morepolymers; and a first plurality of particles encapsulated within thefiber body and a second plurality of particles embedded in an outersurface of the fiber body, wherein the encapsulated first plurality ofparticles comprise an encapsulated particle density, and wherein theencapsulated particle density of the first plurality of particles ishighest proximate an outer surface of the fiber.
 12. A fiber accordingto claim 11, wherein the encapsulated particle density of the firstplurality of particles within the outermost 20% of the volume of thefiber is two times or more the encapsulated particle density of thefirst plurality of particles within the innermost 20% of the volume ofthe fiber.
 13. A fiber according to claim 11, wherein the firstplurality of particles and the second plurality of particles consistessentially of non-polymeric particles.
 14. A fiber according to claim11, wherein the first plurality of particles and the second plurality ofparticles have a maximum size of 100 micrometers or less.
 15. A fiberaccording to claim 11, wherein all of the one or more polymers comprisea melt flow index of 30 or less measured at the conditions specified forthe one or more polymers.
 16. A fiber according to claim 11, wherein allof the one or more polymers comprise a melt flow index of 10 or lessmeasured at the conditions specified for the one or more polymers.
 17. Afiber according to claim 11, wherein all of the one or more polymerscomprise a melt flow index of 1 or less measured at the conditionsspecified for the one or more polymers.
 18. A fiber according to claim11, wherein all of the one or more polymers comprise a melt flow indexof 0.1 or less measured at the conditions specified for the polymers.19. A fiber according to claim 11, wherein the one or more polymers aresemi-crystalline polymers.
 20. A fiber according to claim 19, whereinthe semi-crystalline polymers are nylon.
 21. A method of making aparticulate-loaded polymeric fiber, the method comprising: entraining aplurality of particles within a polymer melt stream; passing the polymermelt stream with the plurality of particles entrained therein through anorifice located within a die, wherein the orifice comprises an entrance,an exit and an interior surface extending from the entrance to the exit,wherein the orifice comprises a semi-hyperbolic converging orifice, andwherein the polymer melt stream enters the orifice at the entrance andleaves the orifice at the exit; delivering lubricant to the orificeseparately from the polymer melt stream, wherein the lubricant isintroduced at the entrance of the orifice; and collecting theparticulate-loaded polymeric fiber comprising the polymer melt streamand a plurality of particles encapsulated within the polymer meltstream, wherein the encapsulated particles comprise an encapsulatedparticle density within the fiber, and wherein the encapsulated particledensity is higher proximate an outer surface of the fiber.
 22. A methodaccording to claim 21, wherein the encapsulated particle density withinthe outermost 20% of the volume of the fiber is two times or more theencapsulated particle density within the innermost 20% of the volume ofthe fiber.
 23. A method according to claim 21, wherein the plurality ofparticles consist essentially of non-polymeric particles.
 24. A methodaccording to claim 21, wherein the polymer melt stream comprises one ormore polymers, and wherein all of the one or more polymers comprise amelt flow index of 30 or less measured at the conditions specified forthe one or more polymers.
 25. A method according to claim 21, whereinthe polymer melt stream comprises one or more polymers, and wherein allof the one or more polymers comprise a melt flow index of 10 or lessmeasured at the conditions specified for the one or more polymers.
 26. Amethod according to claim 21, the polymer melt stream comprises one ormore polymers, and wherein all of the one or more polymers comprise amelt flow index of 1 or less measured at the conditions specified forthe one or more polymers.
 27. A method according to claim 21, whereinall of the one or more polymers comprise a melt flow index of 0.1 orless measured at the conditions specified for the polymers.
 28. A methodaccording to claim 21, wherein the polymer melt stream consistsessentially of one polymer with a melt flow index of 30 or less measuredat the conditions specified for the one or more polymers.
 29. A methodaccording to claim 21, wherein the polymer melt stream consistsessentially of one polymer with a melt flow index of 10 or less measuredat the conditions specified for the one or more polymers.
 30. A methodaccording to claim 21, wherein the polymer melt stream consistsessentially of one polymer with a melt flow index of 1 or less measuredat the conditions specified for the polymer.
 31. A method according toclaim 21, wherein the polymer melt stream consists essentially of onepolymer with a melt flow index of 0.1 or less measured at the conditionsspecified for the polymer.
 32. A method according to claim 21, whereinthe polymer melt stream consists essentially of one or moresemi-crystalline polymers.
 33. A method according to claim 33, whereinthe semi-crystalline polymers are nylon.
 34. A method according to claim21, wherein the polymer melt stream with the plurality of particlesentrained therein is delivered to the entrance of the orifice through anopening that comprises a smaller cross-sectional area than thecross-sectional area of the entrance of the orifice.
 35. A methodaccording to claim 21, wherein delivering the lubricant comprisesdelivering the lubricant through a continuous slot formed about theentrance of the orifice.
 36. A method according to claim 21, whereindelivering the lubricant comprises delivering the lubricant through aplurality of openings located about the entrance of the orifice.
 37. Amethod according to claim 21, wherein at least a portion of thelubricant evaporates from the polymer melt stream after the polymer meltstream leaves the exit of the orifice.
 38. A method according to claim21, wherein the die comprises a plurality of orifices, and wherein themethod further comprises independently delivering the lubricant to eachorifice of the plurality of orifices.
 39. A method according to claim21, wherein collecting the fiber comprises pulling the fiber, whereinthe fiber is elongated during the pulling.
 40. A method according toclaim 21, wherein the average temperature of the polymer melt streampassing into the entrance of the orifice is within 10 degrees Celsius orless above a melt processing temperature of the polymer melt stream. 41.A method according to claim 21, wherein the average temperature of thepolymer melt stream is at or below a melt processing temperature of thepolymer melt stream before the polymer melt stream leaves the exit ofthe orifice.